Cables are used for the transporting energy and information. Often, these cables are very long and even stretch across oceans. Different environments pose different challenges to the cables. When a cable has to cover a long distance, it will face different environments.
In order to determine which cables are best for a particular environment, it would have to be tested in the different environments. This means that the cable would have to be tested against different temperatures, different fluids, different levels of pressure, etc.
For each of these variables, the cable would have to be tested against the varying loads that pass through the cables. Testing any particular type of cable against these variables is very difficult.
Often these cables are wrapped on spools. When wrapped on a spool, a cable is often underneath several layers of itself, and the additional pressure of the mass of the cable and the heat from the layers of cable above and below it can damage the cable.
To test cable, it would have to be taken to the place in which it is to be used, and then subjected to all the environmental factors and varying loads it can be expected to face. This, however, is not practical.
Often these cables are intended to be used at the bottom of the ocean, with salt water, low temperatures and high pressures. Other times cables are used in very frigid environments with extremely low temperatures, high winds, and freezing rain and snow. It is not practical to monitor cable at these locations for extended periods of time under varying power loads.